Which immunohistochemical marker pattern defines a triple-negative breast cancer (TNBC) with basal-like subtype and predicts response to immune checkpoint inhibitors in combination with chemotherapy?
- A ER-/PR-/HER2- with Ki-67 > 20%
- B ER-/PR-/HER2- with high androgen receptor expression
- C ER-/PR-/HER2- with PD-L1 CPS ≥ 10 on immune cells ✓
- D ER-/PR-/HER2- with BRCA1 mutation alone
Correct answer: C. ER-/PR-/HER2- with PD-L1 CPS ≥ 10 on immune cells
Explanation
The KEYNOTE-522 trial established pembrolizumab (PD-1 inhibitor) plus chemotherapy for early TNBC, and the IMpassion130 trial used atezolizumab for metastatic TNBC with PD-L1 positivity defined as combined positive score (CPS) ≥10 on immune cells. PD-L1 CPS ≥10 selects patients most likely to benefit from checkpoint inhibitors. High Ki-67 indicates proliferative disease but does not predict checkpoint inhibitor response. Androgen receptor expression predicts response to antiandrogens (LAR subtype). BRCA mutation predicts PARP inhibitor response.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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